This invention relates to a hydraulic servo steering system for automotive vehicles associated with a source of pressurized fluid which is also utilized for a fluid operating motor under valve control serving a different function from that of the servo steering motor.
According to the disclosure in German patent publication OS No. 23 60 610, an automotive servo steering system is provided in combination with an additional fluid operated device. In such prior art arrangement, both the steering servo motor and the additional operating fluid motor are supplied with a pressurized medium or fluid from a single servo pump. However, priority is given to the servo steering system with respect to the supply of pressurized fluid, although in the neutral position of the steering control valve the pressurized fluid is supplied completely to the additional fluid operated device. On the other hand, when the steering control valve is substantially displaced from the neutral position, flow of the pressurized fluid to the fluid operated device is completely blocked. The additional fluid operated device when hydraulically connected through its control circuit to the fluid reservoir associated with a servo pump, is responsible to cavitation effects in its supply line. Also, in such prior art arrangement, uncontrolled run away operation of the additional fluid operated device is possible under certain conditions. Still further, the cavitation aforementioned may adversely affect the servo steering circuit through the steering control valve.
It is therefore an important object of the present invention to provide a servo steering system in combination with an additional fluid operated device avoiding the disadvantages of the aforementioned prior art arrangements.